Add Liquid::HybridTag

lib/liquid.rb

@@ -57,6 +57,7 @@ require 'liquid/file_system'
 require 'liquid/parser_switching'
 require 'liquid/tag'
 require 'liquid/block'
+require 'liquid/hybrid_tag'
 require 'liquid/parse_tree_visitor'
 require 'liquid/interrupts'
 require 'liquid/tags'

lib/liquid/hybrid_tag.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Liquid
+  class HybridTag < Block
+    def parse(tokens)
+      if tokens.matching_end_tag?(tag_name)
+        @block_form = true
+        super
+      else
+        @block_form = false
+      end
+    end
+
+    def block_form?
+      @block_form
+    end
+
+    def nodelist
+      @body ? @body.nodelist : Const::EMPTY_ARRAY
+    end
+
+    def render_to_output_buffer(context, output)
+      if @block_form
+        render_block_form_to_output_buffer(context, output)
+      else
+        render_self_closing_to_output_buffer(context, output)
+      end
+    end
+
+    private
+
+    def render_block_form_to_output_buffer(_context, _output)
+      raise NotImplementedError, "#{self.class} must implement render_block_form_to_output_buffer"
+    end
+
+    def render_self_closing_to_output_buffer(_context, _output)
+      raise NotImplementedError, "#{self.class} must implement render_self_closing_to_output_buffer"
+    end
+  end
+end

lib/liquid/tokenizer.rb

@@ -9,6 +9,7 @@ module Liquid
     TAG_END = /%\}/
     TAG_OR_VARIABLE_START = /\{[\{\%]/
     NEWLINE = /\n/
+    TAG_NAME_PATTERN = /\A\{%-?\s*(\w+)/
 
     OPEN_CURLEY = "{".ord
     CLOSE_CURLEY = "}".ord
@@ -48,6 +49,49 @@ module Liquid
       token
     end
 
+    def peek
+      @tokens[@offset]
+    end
+
+    def position
+      [@offset, @line_number]
+    end
+
+    def position=(pos)
+      @offset, @line_number = pos
+    end
+
+    # Depth-aware forward scan of pre-tokenized tokens starting from the
+    # current position.
+    def matching_end_tag?(tag_name)
+      end_tag_name = "end#{tag_name}"
+      depth = 0
+      i = @offset
+
+      while i < @tokens.length
+        token = @tokens[i]
+        i += 1
+
+        next unless token.start_with?("{%")
+
+        # TODO: use tag_name
+        match = TAG_NAME_PATTERN.match(token)
+        next unless match
+
+        name = match[1]
+
+        if name == tag_name
+          depth += 1
+        elsif name == end_tag_name
+          return true if depth == 0
+
+          depth -= 1
+        end
+      end
+
+      false
+    end
+
     private
 
     def tokenize